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Length‐Dependent Conductance of Molecular Wires and Contact Resistance in Metal–Molecule–Metal Junctions |
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| Authors: | Hongmei Liu Dr. Nan Wang Dr. Jianwei Zhao Prof. Yan Guo Dr. Xing Yin Dr. Freddy Y. C. Boey Prof. Hua Zhang Prof. |
| Affiliation: | 1. Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210008 (P. R. China), Fax: (+86)?25‐83596523;2. School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore) |
| Abstract: | Molecular wires are covalently bonded to gold electrodes—to form metal–molecule–metal junctions—by functionalizing each end with a ? SH group. The conductance of a wide variety of molecular junctions is studied theoretically by using first‐principles density functional theory (DFT) combined with the nonequilibrium Green′s function (NEGF) formalism. Based on the chain‐length‐dependent conductance of the series of molecular wires, the attenuation factor β is obtained and compared with the experimental data. The β value is quantitatively correlated to the molecular HOMO–LUMO gap. Coupling between the metallic electrode and the molecular bridge plays an important role in electron transport. A contact resistance of 6.0±2.0 KΩ is obtained by extrapolating the molecular‐bridge length to zero. This value is of the same magnitude as the quantum resistance. |
| Keywords: | density functional calculations electron transport energy gap molecular devices tunneling attenuation factor |